--- a/mercurial/thirdparty/concurrent/futures/process.py Wed Mar 02 10:24:49 2022 -0500
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,365 +0,0 @@
-# Copyright 2009 Brian Quinlan. All Rights Reserved.
-# Licensed to PSF under a Contributor Agreement.
-
-"""Implements ProcessPoolExecutor.
-
-The follow diagram and text describe the data-flow through the system:
-
-|======================= In-process =====================|== Out-of-process ==|
-
-+----------+ +----------+ +--------+ +-----------+ +---------+
-| | => | Work Ids | => | | => | Call Q | => | |
-| | +----------+ | | +-----------+ | |
-| | | ... | | | | ... | | |
-| | | 6 | | | | 5, call() | | |
-| | | 7 | | | | ... | | |
-| Process | | ... | | Local | +-----------+ | Process |
-| Pool | +----------+ | Worker | | #1..n |
-| Executor | | Thread | | |
-| | +----------- + | | +-----------+ | |
-| | <=> | Work Items | <=> | | <= | Result Q | <= | |
-| | +------------+ | | +-----------+ | |
-| | | 6: call() | | | | ... | | |
-| | | future | | | | 4, result | | |
-| | | ... | | | | 3, except | | |
-+----------+ +------------+ +--------+ +-----------+ +---------+
-
-Executor.submit() called:
-- creates a uniquely numbered _WorkItem and adds it to the "Work Items" dict
-- adds the id of the _WorkItem to the "Work Ids" queue
-
-Local worker thread:
-- reads work ids from the "Work Ids" queue and looks up the corresponding
- WorkItem from the "Work Items" dict: if the work item has been cancelled then
- it is simply removed from the dict, otherwise it is repackaged as a
- _CallItem and put in the "Call Q". New _CallItems are put in the "Call Q"
- until "Call Q" is full. NOTE: the size of the "Call Q" is kept small because
- calls placed in the "Call Q" can no longer be cancelled with Future.cancel().
-- reads _ResultItems from "Result Q", updates the future stored in the
- "Work Items" dict and deletes the dict entry
-
-Process #1..n:
-- reads _CallItems from "Call Q", executes the calls, and puts the resulting
- _ResultItems in "Request Q"
-"""
-
-from __future__ import absolute_import
-
-import atexit
-from . import _base
-import Queue as queue
-import multiprocessing
-import threading
-import weakref
-import sys
-
-__author__ = 'Brian Quinlan (brian@sweetapp.com)'
-
-# Workers are created as daemon threads and processes. This is done to allow the
-# interpreter to exit when there are still idle processes in a
-# ProcessPoolExecutor's process pool (i.e. shutdown() was not called). However,
-# allowing workers to die with the interpreter has two undesirable properties:
-# - The workers would still be running during interpretor shutdown,
-# meaning that they would fail in unpredictable ways.
-# - The workers could be killed while evaluating a work item, which could
-# be bad if the callable being evaluated has external side-effects e.g.
-# writing to a file.
-#
-# To work around this problem, an exit handler is installed which tells the
-# workers to exit when their work queues are empty and then waits until the
-# threads/processes finish.
-
-_threads_queues = weakref.WeakKeyDictionary()
-_shutdown = False
-
-def _python_exit():
- global _shutdown
- _shutdown = True
- items = list(_threads_queues.items()) if _threads_queues else ()
- for t, q in items:
- q.put(None)
- for t, q in items:
- t.join(sys.maxint)
-
-# Controls how many more calls than processes will be queued in the call queue.
-# A smaller number will mean that processes spend more time idle waiting for
-# work while a larger number will make Future.cancel() succeed less frequently
-# (Futures in the call queue cannot be cancelled).
-EXTRA_QUEUED_CALLS = 1
-
-class _WorkItem(object):
- def __init__(self, future, fn, args, kwargs):
- self.future = future
- self.fn = fn
- self.args = args
- self.kwargs = kwargs
-
-class _ResultItem(object):
- def __init__(self, work_id, exception=None, result=None):
- self.work_id = work_id
- self.exception = exception
- self.result = result
-
-class _CallItem(object):
- def __init__(self, work_id, fn, args, kwargs):
- self.work_id = work_id
- self.fn = fn
- self.args = args
- self.kwargs = kwargs
-
-def _process_worker(call_queue, result_queue):
- """Evaluates calls from call_queue and places the results in result_queue.
-
- This worker is run in a separate process.
-
- Args:
- call_queue: A multiprocessing.Queue of _CallItems that will be read and
- evaluated by the worker.
- result_queue: A multiprocessing.Queue of _ResultItems that will written
- to by the worker.
- shutdown: A multiprocessing.Event that will be set as a signal to the
- worker that it should exit when call_queue is empty.
- """
- while True:
- call_item = call_queue.get(block=True)
- if call_item is None:
- # Wake up queue management thread
- result_queue.put(None)
- return
- try:
- r = call_item.fn(*call_item.args, **call_item.kwargs)
- except:
- e = sys.exc_info()[1]
- result_queue.put(_ResultItem(call_item.work_id,
- exception=e))
- else:
- result_queue.put(_ResultItem(call_item.work_id,
- result=r))
-
-def _add_call_item_to_queue(pending_work_items,
- work_ids,
- call_queue):
- """Fills call_queue with _WorkItems from pending_work_items.
-
- This function never blocks.
-
- Args:
- pending_work_items: A dict mapping work ids to _WorkItems e.g.
- {5: <_WorkItem...>, 6: <_WorkItem...>, ...}
- work_ids: A queue.Queue of work ids e.g. Queue([5, 6, ...]). Work ids
- are consumed and the corresponding _WorkItems from
- pending_work_items are transformed into _CallItems and put in
- call_queue.
- call_queue: A multiprocessing.Queue that will be filled with _CallItems
- derived from _WorkItems.
- """
- while True:
- if call_queue.full():
- return
- try:
- work_id = work_ids.get(block=False)
- except queue.Empty:
- return
- else:
- work_item = pending_work_items[work_id]
-
- if work_item.future.set_running_or_notify_cancel():
- call_queue.put(_CallItem(work_id,
- work_item.fn,
- work_item.args,
- work_item.kwargs),
- block=True)
- else:
- del pending_work_items[work_id]
- continue
-
-def _queue_management_worker(executor_reference,
- processes,
- pending_work_items,
- work_ids_queue,
- call_queue,
- result_queue):
- """Manages the communication between this process and the worker processes.
-
- This function is run in a local thread.
-
- Args:
- executor_reference: A weakref.ref to the ProcessPoolExecutor that owns
- this thread. Used to determine if the ProcessPoolExecutor has been
- garbage collected and that this function can exit.
- process: A list of the multiprocessing.Process instances used as
- workers.
- pending_work_items: A dict mapping work ids to _WorkItems e.g.
- {5: <_WorkItem...>, 6: <_WorkItem...>, ...}
- work_ids_queue: A queue.Queue of work ids e.g. Queue([5, 6, ...]).
- call_queue: A multiprocessing.Queue that will be filled with _CallItems
- derived from _WorkItems for processing by the process workers.
- result_queue: A multiprocessing.Queue of _ResultItems generated by the
- process workers.
- """
- nb_shutdown_processes = [0]
- def shutdown_one_process():
- """Tell a worker to terminate, which will in turn wake us again"""
- call_queue.put(None)
- nb_shutdown_processes[0] += 1
- while True:
- _add_call_item_to_queue(pending_work_items,
- work_ids_queue,
- call_queue)
-
- result_item = result_queue.get(block=True)
- if result_item is not None:
- work_item = pending_work_items[result_item.work_id]
- del pending_work_items[result_item.work_id]
-
- if result_item.exception:
- work_item.future.set_exception(result_item.exception)
- else:
- work_item.future.set_result(result_item.result)
- # Delete references to object. See issue16284
- del work_item
- # Check whether we should start shutting down.
- executor = executor_reference()
- # No more work items can be added if:
- # - The interpreter is shutting down OR
- # - The executor that owns this worker has been collected OR
- # - The executor that owns this worker has been shutdown.
- if _shutdown or executor is None or executor._shutdown_thread:
- # Since no new work items can be added, it is safe to shutdown
- # this thread if there are no pending work items.
- if not pending_work_items:
- while nb_shutdown_processes[0] < len(processes):
- shutdown_one_process()
- # If .join() is not called on the created processes then
- # some multiprocessing.Queue methods may deadlock on Mac OS
- # X.
- for p in processes:
- p.join()
- call_queue.close()
- return
- del executor
-
-_system_limits_checked = False
-_system_limited = None
-def _check_system_limits():
- global _system_limits_checked, _system_limited
- if _system_limits_checked:
- if _system_limited:
- raise NotImplementedError(_system_limited)
- _system_limits_checked = True
- try:
- import os
- nsems_max = os.sysconf("SC_SEM_NSEMS_MAX")
- except (AttributeError, ValueError):
- # sysconf not available or setting not available
- return
- if nsems_max == -1:
- # indetermine limit, assume that limit is determined
- # by available memory only
- return
- if nsems_max >= 256:
- # minimum number of semaphores available
- # according to POSIX
- return
- _system_limited = "system provides too few semaphores (%d available, 256 necessary)" % nsems_max
- raise NotImplementedError(_system_limited)
-
-
-class ProcessPoolExecutor(_base.Executor):
- def __init__(self, max_workers=None):
- """Initializes a new ProcessPoolExecutor instance.
-
- Args:
- max_workers: The maximum number of processes that can be used to
- execute the given calls. If None or not given then as many
- worker processes will be created as the machine has processors.
- """
- _check_system_limits()
-
- if max_workers is None:
- self._max_workers = multiprocessing.cpu_count()
- else:
- if max_workers <= 0:
- raise ValueError("max_workers must be greater than 0")
-
- self._max_workers = max_workers
-
- # Make the call queue slightly larger than the number of processes to
- # prevent the worker processes from idling. But don't make it too big
- # because futures in the call queue cannot be cancelled.
- self._call_queue = multiprocessing.Queue(self._max_workers +
- EXTRA_QUEUED_CALLS)
- self._result_queue = multiprocessing.Queue()
- self._work_ids = queue.Queue()
- self._queue_management_thread = None
- self._processes = set()
-
- # Shutdown is a two-step process.
- self._shutdown_thread = False
- self._shutdown_lock = threading.Lock()
- self._queue_count = 0
- self._pending_work_items = {}
-
- def _start_queue_management_thread(self):
- # When the executor gets lost, the weakref callback will wake up
- # the queue management thread.
- def weakref_cb(_, q=self._result_queue):
- q.put(None)
- if self._queue_management_thread is None:
- self._queue_management_thread = threading.Thread(
- target=_queue_management_worker,
- args=(weakref.ref(self, weakref_cb),
- self._processes,
- self._pending_work_items,
- self._work_ids,
- self._call_queue,
- self._result_queue))
- self._queue_management_thread.daemon = True
- self._queue_management_thread.start()
- _threads_queues[self._queue_management_thread] = self._result_queue
-
- def _adjust_process_count(self):
- for _ in range(len(self._processes), self._max_workers):
- p = multiprocessing.Process(
- target=_process_worker,
- args=(self._call_queue,
- self._result_queue))
- p.start()
- self._processes.add(p)
-
- def submit(self, fn, *args, **kwargs):
- with self._shutdown_lock:
- if self._shutdown_thread:
- raise RuntimeError('cannot schedule new futures after shutdown')
-
- f = _base.Future()
- w = _WorkItem(f, fn, args, kwargs)
-
- self._pending_work_items[self._queue_count] = w
- self._work_ids.put(self._queue_count)
- self._queue_count += 1
- # Wake up queue management thread
- self._result_queue.put(None)
-
- self._start_queue_management_thread()
- self._adjust_process_count()
- return f
- submit.__doc__ = _base.Executor.submit.__doc__
-
- def shutdown(self, wait=True):
- with self._shutdown_lock:
- self._shutdown_thread = True
- if self._queue_management_thread:
- # Wake up queue management thread
- self._result_queue.put(None)
- if wait:
- self._queue_management_thread.join(sys.maxint)
- # To reduce the risk of openning too many files, remove references to
- # objects that use file descriptors.
- self._queue_management_thread = None
- self._call_queue = None
- self._result_queue = None
- self._processes = None
- shutdown.__doc__ = _base.Executor.shutdown.__doc__
-
-atexit.register(_python_exit)